A clasp corresponding to the generic definition which has just been given is described in the Swiss patent document CH-A-568 035 (=U.S.-A-No. 3,913,182). This clasp, developed in particular for a watch bracket, includes two rigid elements fixed to the free ends of the bracelet. One of the elements includes a hook which may be inserted through an opening presented by the other element. Such other element includes a catch arranged to latch the hook when the elements are pressed against one another. The catch includes a push button emerging from the other element which when it is pressed by a finger enables unlatching the elements and opening the clasp.
A clasp showing much analogy with that just described hereinabove is described in the German patent document DE-A-35 20 122. In addition to the latching system employing a hook and a catch arranged as described hereinabove, the clasp offers the possibility of being extended beyond the simple extension provided by the opening of two blades articulated on one another, and this in view of the fact that one of the blades is mounted to slide in a stirrup itself mounted on a hinge on the other blade.
The Swiss patent document CH-A-553 553 describes a clasp enabling the shortening or lengthening of a bracelet. To this end it is provided with a movable plate sliding under a fixed plate, each of the plates being provided with holes superposed in pairs. In one pair of holes there may penetrate a hook, the beak of which is arranged in the longitudinal direction of the bracelet. In order to open the clasp, one presses on a push button in the longitudinal sense of the bracelet. This arrangement is not in any way adapted to the clasp of the present invention. Moreover, the construction does not provide a fine adjustement, but a coarse adjustment extending at least over the width of a link.
However, none of the cited documents offers the possibility of shortening or extending slightly the length of the bracelet in order to permit wearing the bracelet tightly or loosely around the arm which bears it. Nevertheless, it has been determined that one frequently experiences the need to proceed with such an adjustment since the dimensions of the arm change according to whether the external temperature is low or high. With no possibility of regulation, the bracelet may squeeze the wrist at high temperatures during summer time. On the other hand, during winter, the same bracelet is free around the wrist and if it is employed to attach a watch, the latter may assume undesired positions, for example under the wrist. It has likewise been determined that the differences between the dimensions of a swollen or contracted wrist of the same person is less than the usual width of the links making up the bracelet. From this it is evident that adding or removing a normal link from the bracelet is not entirely satisfactory. Some manufacturers propose half links to overcome such difficulty, however this solution is unsatisfactory from the point of view of the appearance as well as being expensive and difficult to practise by the wearer of the bracelet.